Pulse-forming circuits including a plurality of transmission lines



Nov. 24, 1964 M. w. BROOKSBY PULSE-FORMING CIRCUITS INCLUDING APLURALITY OF TRANSMISSION LINES Filed Jan. 11, 1963 THKV INPUT Figure 2INVENTOR MERRILL w. BROOKSBY BY ATTORNEY United States Patent UTTE resission o, Quilt a. to El2W- Alto, a corporation This invention relatesto a circuit for producing high energy pulses at extremely hi hrepetition rates and more particularly to a circuit which produces highpower output pulses from an applied high frequency signal.

It is a principal obiect of the present invention to provide an improvedpulse-formin circuit which operates at frequencies up to several hundredmcgacycles per second.

In accordance with a preferred embodiment of the invention, a triggercircuit of the ope known as a Schmitt trigger is connected to recei eapp d signals and has each or" its outputs connected to an input of adifferential amplifier. The outputs of the amplifier are combined anddirTerentiated using a system of transmission lines.

For an understanding of the principles or the invention, reference ismade to the following description of the invention as illustrated in theaccompanying drawing in which:

FIGURE 1 shows a schematic diagram of a preferred embodiment of thepulse-forming circuit, and

FIGURE 2 is a schematic diagram or" the pulse-forming circuit for use inlower frequency a -lcations.

Referring to the circuit of PIGURL 1, input signal is applied totransistor 9 of trigger circuit 11. Transistors 9 and 13 are connectedto he alternately conductive and nonconductive in opposite phaserelationship. Each time the signal at the input of trigger circuit 11passes in one direction through a reference level, transistor 9 becomesconductive producing an output pulse on line 17 and causing transistor33 to become nonconductive, thereby producing an output pulse ofopposite polarity on line Each time the input signal passes in theopposite direction through the reference level transistor 13 becomesconductive prorlucing an output pulse on line 15 and causing transistor9 to become nonconductive, thereby producing an output pulse or"opposite polarity on line 1'7. Thus, for alternating signal applied toLie input of trigger circuit ll, pulses of given polarity appearalternately on lines 15 and 17.

hese pulses appear across resistors l? and and are applied to the baseelectrodes 23 and 25 of transistors 27 and 29. The commonly connectedemitter electrodes of these transistors are connected to ground throughresistor 31. The collector electrodes of the transistors 27 and 29 areconnected to the inputs to the system of transmission lines 33. Thesetransmission lines are substantially lossless devices which provideimpedance transformation between inputs and output over a specifiedrange of frequencies above DC. Current steps of equal amp' tude andopposite direction are supplied from these collector electrodes to thelines and 37. This produces voltage steps of opposite polarities whichpropagate toward the load 43.. The ends or" the transmission lines 35and 37 remote from the input ends are so connected that these voltagesteps are combined in parallel across the load 41. The characteristicimpedance of each of the lines 35 and 37 is chosen to be four times theimpedance of the load 41 and twice the characteristic impedance of line39. Because of the impedance mismatch which these original or incidentpropagating waves encounter at the load, reflected waves are produced.These waves are of opposite polarity and are one-hflf the amplitude ofthe original or incident wave and are reflected back down lines 35 and37. At the same time a wave of the same polarity and of one half theamplitude of the original or incident wave propa- '1 1 resented Nov.

gates down line 39. Also at the same time, a voltage having an amplitudeof one-half of the original or incident wave appears across load 41.

The waves appearing on lines 55, 37 and 39 at the ends remote from theinput ends of the loss all propagate with uniform velocity toward theinput ends. The voltage of one-half the amplitude of the original orincident wave is maintained across load ll during the propagation timesof the reflected waves on lines 35, 37 and 39. When the wave on line 39reaches the shorted end, a wave of opposite polarity and of equalamplitude is reflected back toward load 41. At the same time thereflected waves in lines 35 37 reach the input end, which ends appear asopen circuits because of the relatively high collector impedances oftransistors 27 and 29. As a result, a wave appears on each of lines 35and 37 which is reflected back toward load ll and which has the samepolarity and twice the amplitude of the wave which was reflected fromthe load 41 toward the input ends. In other words, these secondreflected waves on lines 35 and 37 are equal in amplitude and oppositein polarity to the original or incident waves. When these secondreflected waves on lines 35 and 37 and the reflecte wave on line 39simultaneously reach load-i l, the original or incident waves arecancelled output voltage across the load 41 goes to zero. The voltagewave on line 39 reflected back from the shorted end prohibits furtherreflections in the transmission lines. The duration of the output pulseis thus twice the propagation time of the lines 35, 3'7 and 3?, whichpropagation time is established by the length of the lines. The rise andfall times of the output ulse across load 41 are thus equal to the risetime of the applied current steps. For the impedance relationships asshown, the collector-to-collector im edance presented by thetransmission lines 33 to the transistors 2? and 29 is eight times theimpedance of load 41 for the duration of the pulse and is zerothereafter. Also for the impedance relationships as shown overshoot,undershoot, pulse sag and ringing of the leading and trailing edges arethus eliminated. These transmission lines therefore provide pulseshaping in addition to impedance transformation for the duration of theraise.

PlGURl-E 2 shows a circuit for use in lower frequency applications andwhich uses another type of electromagetic induction apparatus, namelytransformer 43, the output stage. This transformer has a pair ofwindings 25 and 47 which have dot-polarity marki gs as shown and whichare so connected that current pulses of opposite polarity appliedthereto combine to increase the total magnetic flux in the transformer.A load 13 connected across one winding 47 is reflected into the circuitconnected to the other winding 45 and thus serves as the load for eachof transistors 27 and 29. The pulse power available rom each of theoutputs of the trigger circuit 11 is thus combined in transformer 43 andis delivered to the load 49. it can be seen that a difierentialtransformer having a center-tapped primary winding connected to thecollector electrodes of transistors 27 and 29 and having the secondarywinding connected to the load 49 may also be used in place or" thetransmission lines 33 in lower frequency applications. A transformerthus connected combines the differential pulses from the transistors 27and 29 and matches the impedances of the load 49 and the drivingcircuit.

I claim:

1. A pulse-forming circuit comprising:

a trigger circuit having a pair of outputs and being operative only ineither one of two operating states; means to apply signal to saidtrigger circuit to produce changes in the operating states thereof;

said trigger circuit producing signals in phase opposition at theoutputs thereof in response to changes in the operating states thereof;

a pair of transmission lines each having an input end and an output end;

means connecting the outputs of said trigger circuitta the inputs ofsaid transmission lines;

a utilization circuit;

means connecting the output ends of said lines in parallel across saidutilization circuit for applying the signals appearing at the input endsof the transmission lines to said utilization circuit in in-phaserelationship;

another transmission line having an input end and a shorted end remotefrom said input end;

and means connecting the input end of said other transmission lineacross said utilization circuit.

2. A pulse-forming circuit comprising:

a trigger circuit having a pair of outputs and being operative only ineither one of two operating states; means to apply signal to saidtrigger circuit to produce changes in the operating states thereof;

said trigger circuit producing signals in phase opposition at theoutputs'thereof in response to changesin the operating states thereof;

a pair of transmission lines each having an input end and an output end;

means connecting the outputs of said trigger circuit to inputs of saidtransmission lines;

a utilization circuit;

means connecting the output ends of said lines in parallel across saidutilization circuit for applying the signals appearing at the input endsof the transmission lines to said utilization circuit in in-phaserelationship;

another transmission line including a conductor from each of said pairof transmission lines and having an input end and a shorted end remotefrom said input end; I

and means connecting the input endof said other transmission line acrosssaid utilization circuit.

3. In a pulse-forming circuit:

a plurality of conductors forming at least a pair of transmission lines,each of said lines having an input end and an output end;

means to apply signals to the input ends of said transmission lines inphase opposition;

a utilization circuit;

means connecting the output ends of said lines in parallel across saidutilization circuit for applying the signals appearing at the input endsof the transmission lines to said utilization circuit in in-phaserelationship; 7

another transmission line having an input end and a shorted end remotefrom said input end;

and means connecting the input end of said other transmission lineacross said utilization circuit.

4. In a pulse-forming circuit:

a plurality of conductors forming at least a pair of transmission lines,each of said lines having an input end and an output end;

means to apply signals to the input ends of said transmission lines inphase opposition;

a utilization circuit;

means connecting the output ends of said lines in par allel across saidutilization circuit for applying the signals appearing at the input endsof the transmission lines to said utilization circuit in in-phaserelationship;

another transmission line including a conductor of each of saidtransmission lines and having an input end 7 and a shorted end remotefrom said input end;

and means connecting the input end of said other transmission lineacross said utilization circuit.

5. in a pulse-forming circuit;

a plurality of conductors forming at least a pair of transmission lines,each of said lines having an input end and an output end;

means to apply signals to the input ends of said transmission lines inphase opposition;

a utilization circuit; 7

means connecting the output ends of said lines in parallel across saidutilization c rcuit for applying the signals appearing at the input endsof the transmission lines to said util zation circuit in in-phaserelationship;

another transmission line including a conductor of each of saidtransmission lines;

said'other transmission line having a characteristic impedance whichis'less than the characteristic impedance of each of said pm'r oftransmission lines and having an input end and a shorted end remote fromsaid input end;

and means connecting the input end of said other transmission lineacross said utilization circuit.

din a pulse-forming circuit:

a plurality of conductors forming at least a pair of transmission lines,each of said lines having an input end and an output end;

means to apply signals to the input ends of said trans" mission lines inphase opposition; a utilization circuit;

means connecting the output ends of said lines in par-- allel acrosssaid utilization circuit for applying the signals appearing at the inputends of the transmission lines to said utilization circuit in in-phaserelationship;

another transmission line including a conductor of each of saidtransmission lines;

said other transmission line having a characteristic impedance which istwice the impedance of said utilization circuit and having an input endanda shorted end remote from said input end, 7

the characteristic impedance of each of said pair of transnussion linesbeing twice the characteristic impedance of said other transmissionline;

and means connecting the input end of said other transmissionilineacross said utilization circuit.

7. In a pulse-forming circuit:

a plurality of conductors forming at least a pair of transmission lines,each of said lines having an input end and an output end;

means to apply signals to the input ends of said transmission lines inphase opposition;

a utilization circuit; v

means connecting the output ends of said lines in parallel across saidutilization circuit for applying: the signals appearing at the inputends of the transmission lines to said utilization circuit in in-phaserelationship; a

another transmission line including a conductor of each of said pair oftransmission lines and having an input end and a shorted end remote fromsaid input end;

each of said pair of transmission lines and said other transmission linehaving the same propagation delay time;

and means connecting the input end of said other transmission lineacross said utilization circuit.

References Cited by the Examiner UNITED STATES PATENTS 2,966,640 12/60Eiland 33326 3,031,588 4/62 Hilsenrath 307--88.5 3,996,445 7/63 Herzog307-885 ARTHUR GAUSS, Primary Examiner.

1. A PULSE-FORMING CIRCUIT COMPRISING: A TRIGGER CIRCUIT HAVING A PAIROF OUTPUTS AND BEING OPERATIVE ONLY IN EITHER ONE OF TWO OPERATINGSTATES; MEANS TO APPLY SIGNAL TO SAID TRIGGER CIRCUIT TO PRODUCE CHANGESIN THE OPERATING STATES THEREOF; SAID TRIGGER CIRCUIT PRODUCING SIGNALSIN PHASE OPPOSITION AT THE OUTPUTS THEREOF IN RESPONSE TO CHANGES IN THEOPERATING STATES THEREOF; A PAIR OF TRANSMISSION LINES EACH HAVING ANINPUT END AND AN OUTPUT END; MEANS CONNECTING THE OUTPUTS OF SAIDTRIGGER CIRCUIT TO THE INPUTS OF SAID TRANSMISSION LINES; A UTILIZATIONCIRCUIT; MEANS CONNECTING THE OUTPUT ENDS OF SAID LINES IN PARALLELACROSS SAID UTILIZATION CIRCUIT FOR APPLYING THE SIGNALS APPEARING ATTHE INPUT ENDS OF THE TRANSMISSION LINES TO SAID UTILIZATION CIRCUIT ININ-PHASE RELATIONSHIP; ANOTHER TRANSMISSION LINE HAVING AN INPUT END ANDA SHORTED END REMOTE FROM SAID INPUT END; AND MEANS CONNECTING THE INPUTEND OF SAID OTHER TRANSMISSION LINE ACROSS SAID UTILIZATION CIRCUIT.